The internal shield of an anastomosis in accordance with the invention solves the problem of the origin of so-called intimo-medial hyperplasia, which quite often develops in an anastomosis in a vascular system, particularly in the case of vascular reconstructions of smaller caliber, and leads to a resulting occlusion of the reconstruction.
The anastomosis in the vascular system is basically an artificially created connection either of actual vessels or of an actual vessel and a biological or artificial arterial substitute vessel, and most commonly is executed by suturing with the use of a special suturing material. Such anastomosis can be created in any part of the vascular system regardless of its caliber. In most cases, the connection from end to side is desirable or preferred.
In the case of anastomoses in small caliber areas, which generally means diameters up to 6 mm (for example the reconstruction of coronary arteries ), there exists a certain problem, occurring relatively often after some time period, usually after several months, and having no dependence on the technical quality of the performed anastomosis. It is the phenomenon standardly described as intimo-medial hyperplasia. This means that in the connection, most commonly in the apex of the anastomosis, a mound gradually develops consisting of the structures of the hyperplastic intima and media of the targeted vessel, that is the vessel on which the connection is created in the direction of blood flow. The situation is best illustrated in FIG. 1., which is a schematic drawing of an anastomosis of the vessel 1 and an in-flowing vascular substitute 2, end to side. The intimo-medial hyperplasia 3 is illustrated in a typical location; and the blood flow is indicated by the arrows. This gradually growing structure 3a,3b understandably leads to the stenosis of the cross-section of the reconstruction, reduction of the blood flow, and ultimately to complete occlusion.
The generally accepted theory of the development of this phenomenon is as follows: the created anastomosis disturbs, in dependence on different circumstances, the different characteristics of blood flow, most commonly so-called stability of the flow, which is expressed by Reynolds' number. The anastomosis also disturbs the normal laminar flow toward turbulence. In a direct relation, higher turbulence also means a higher quantity of liberated energy. The forces which activate the perivascular transfer of the energy by vibration across the vascular wall are simultaneously the cause of the chronic stress and damage of the surrounding tissue, and at the same time, initiate the response of biochemical mediators, and in their ultimate effect lead to the gradual development of the intimo-medial hyperplasia
At the present time, there is no known method, in the accessible literature, which could prevent this undesirable biological process with some degree of reliability. The most common preventive measure is the creation of a maximally wide anastomosis. This possibility is, of course, objectively limited by the caliber of connected tubes, either vessels or vessel and substitute.